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Date: Wed, 1 Oct 2014 11:29:43 -0700 From: Prashant <prashant@...adcom.com> To: Eric Dumazet <eric.dumazet@...il.com> CC: David Miller <davem@...emloft.net>, <bpoirier@...e.de>, <mchan@...adcom.com>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: Re: [PATCH net v6 4/4] tg3: Fix tx_pending checks for tg3_tso_bug On 9/30/2014 9:24 PM, Eric Dumazet wrote: > On Tue, 2014-09-30 at 20:14 -0700, Prashant wrote: > >> Sorry about the late reply, out of all the HW bug conditions checked in >> tg3_tx_frag_set() the most frequently hit condition is the short 8 byte >> dma bug, where the chip cannot handle TX descriptors whose data buffer >> is 8 bytes or less. Most of the LSO skb's given to the driver has their >> fragments filled upto PAGE_SIZE (expect the last fragment depending on >> skb->len). And if such a LSO skb's last fragment meets the 8 bytes HW >> bug condition the above routine will not help workaround this particular >> case. > > Thats pretty easy to work around. > > Say rebuilt skb has N frags (N > 1 given your description) > > They are numbered 0, ... N-2, N-1 > > Instead of filling N-2 completely, fill it to PAGE_SIZE-8, so that last > frag has at least 8 bytes in it. definitely it can be tweaked to match what is needed with additional workarounds. > > Also take a look at commit 2e4e44107176d552f8bb1bb76053e850e3809841 > ("net: add alloc_skb_with_frags() helper") > > This helper is much modular/flexible than the initial proposed one. Thanks. > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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